Golgappa.net | Golgappa.org | BagIndia.net | BodyIndia.Com | CabIndia.net | CarsBikes.net | CarsBikes.org | CashIndia.net | ConsumerIndia.net | CookingIndia.net | DataIndia.net | DealIndia.net | EmailIndia.net | FirstTablet.com | FirstTourist.com | ForsaleIndia.net | IndiaBody.Com | IndiaCab.net | IndiaCash.net | IndiaModel.net | KidForum.net | OfficeIndia.net | PaysIndia.com | RestaurantIndia.net | RestaurantsIndia.net | SaleForum.net | SellForum.net | SoldIndia.com | StarIndia.net | TomatoCab.com | TomatoCabs.com | TownIndia.com
Interested to Buy Any Domain ? << Click Here >> for more details...

  1. Categories >> Software >> Databases >> SQL PLSQL
  2. Suggest New Category

what is difference between "Primary key" and "Unique key"?

Question Posted / swapna

Answers were Sorted based on User's Feedback



what is difference between "Primary key" and "Unique key"?..

Answer / swapna

1)unique key can be null but primariy key cant be null.
2)primariy key can be refrenced to other table as FK.
Primary key and unique are Entity integrity constraints
Primary key allows each row in a table to be uniquely
identified and ensures that no duplicate rows
exist and no null values are entered.
Unique key constraint is used to prevent the duplication of
key values within the rows of a table and allow null
values. (In oracle, one null is not equal to another null).

Is This Answer Correct ?    4 Yes 0 No

what is difference between "Primary key" and "Unique key"?..

Answer / satya_k21

Hi,

Primary Key: Not Null+ unique.but it wont allows null
values.

Unique: It allows null values , but it should be unique.

Regards,
Satya.k

Is This Answer Correct ?    3 Yes 0 No

what is difference between "Primary key" and "Unique key"?..

Answer / nitin gupta

Uniques: Enforce unique data in the database
it allows row containing null value but only once
It implements non clustered index.

primary key: Enforce unique data in the database
it don't allow any record containing null value
it implements clustered index (data physically
sorted)

Is This Answer Correct ?    3 Yes 0 No

what is difference between "Primary key" and "Unique key"?..

Answer / kk

PRIMARY KEY=UNIQUE KEY+ NOT NULL KEY so its a combo drive

Is This Answer Correct ?    1 Yes 2 No

Post New Answer

More SQL PLSQL Interview Questions

in sql table following column r there i want find 1st paid ,2nd paid,3rd paid date for same |service_type|date |vehicle_no| |------------|------|_---------| |paid |23 jan|MH12H2007 | | | | | |paid |26 feb|MH12H2007 | | | | | | | | | |paid |28 mar|MH12H2007 | i want o/p like below vehicle no| 1st paid date | 2nd paid date|3rd paid |latest paid date| pls help me out

4 Answers  

What are the advantages of pl sql over sql?

0 Answers  

Differentiate between syntax and runtime errors.

0 Answers  

What is relationship? How many types of relationship are there?

0 Answers  

What are the sql versions?

0 Answers  

what is clause? : Sql dba

0 Answers  

how to create user in sql and how to set password for that?

3 Answers  

how to retrieve only duplicate values in a table

9 Answers  

What are Lexical Parameters.How They are used in Reports 6i

2 Answers   eicc,

Is sqlite free?

0 Answers  

Is sql a oracle?

0 Answers  

Who developed sql?

0 Answers  

For more SQL PLSQL Interview Questions Click Here
Categories